Stereoscopy (also called stereoscopics or three-dimensional (3D) imaging) is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision. Originally, stereograms created by such techniques involved a pair of stereo images which could be viewed using a stereoscope. Most stereoscopic methods present two offset images separately to the left and right eye of the viewer. These two-dimensional images may then be combined in the brain to give the perception of three-dimensional depth. In other words, stereoscopy creates the illusion of three-dimensional depth from using two-dimensional images. Stereoscopy may thus be distinguished from three-dimensional displays that display an image in three full dimensions, allowing the observer to increase information about the 3-dimensional objects being displayed by head and eye movements.
To create the illusion of a three-dimensional effect, another method employs a binocular imaging technique, for example, with two cameras disposed eye distance apart. With this method, the three-dimensional impression gained by the observer may be produced by the fact that the two imaging channels work in different colors, with the observer wearing special glasses, of which one glass is tinted in one color, while the other glass is tinted with a different color. Similar techniques may use polarized light and suitably polarized glasses. Although this kind of three-dimensional imaging exhibits higher information content, it does not go beyond the sum of the information content of two two-dimensional images received from the two imaging elements. Again, the observer is offered merely a three-dimensional impression corresponding to that gained by an observer who is fixed in relation to an actual three-dimensional object.
Another method for producing images with a three-dimensional effect is based on holography. In this method, a three-dimensional object is illuminated by a viewing beam, such as a laser beam, with the light reflected by the object being mixed with a reference beam, also often generated by a laser beam. The resulting interference pattern of the two beams may be stored as a holographic recording so that, with suitable lighting, the developed holographic recording may be recovered and projected to provide images having a three-dimensional impression. With holographic imaging, the three-dimensional impression may be more complete because, due to the holographic recording technique, the observer may be able to go “round the object” since the surface of the imaged object appears to hover freely in space.
Three-dimensional effects may also be creating in moving images. A three-dimensional (3D) film or stereoscopic three-dimensional (S3D) film involves a motion picture that enhances the illusion of three-dimensional depth perception. Derived from stereoscopic photography, a regular motion picture camera system may be used to record images as seen from two perspectives, or computer-generated imagery may be used to generate the two perspectives in post-production to create the film as a series of moving images. Special projection hardware and/or eyewear may then be used to provide the illusion of three-dimensional depth when viewing the film. In addition to being used in theatrical film releases, television broadcasts and direct-to-video films may also incorporate similar methods such as in the case of three-dimensional (3D) television and Blu-ray three-dimensional (3D) video.